All the home runs in the third inning were hit off Blazek (0-1), who was making his first major league start following 108 appearances in relief.

"I felt like I made some decent pitches but they were locked in on everything," the right-hander said. "It's not how I pictured it going."

He could have hardly imagined becoming the first pitcher in baseball history to allow five home runs in an inning.

Only five other major league teams hit five homers in an inning, a feat that had not occurred since Milwaukee did it in 2006. Washington became the eighth team to hit four in a row, the first since Arizona in 2010.

After Harper connected in the first inning, Brian Goodwin started the long-ball party in the third with a two-run drive after Blazek walked Washington starter Max Scherzer.

"The last thing I wanted to do was lead off the inning with a walk, especially to a pitcher," Blazek said. "It just kept building and building from there."

Wilmer Difo, Harper and Zimmerman followed with long home runs.

The streak was interrupted when Daniel Murphy flied out, after which some of the fans reacted with good-natured booing.

Anthony Rendon resumed the fun with a shot to dead center that finally chased Blazek, who gave up seven hits — six of them long balls.

Zimmerman and Jose Lobaton both homered off Wily Peralta in the fourth for a 15-1 lead.

The eight home runs tied the franchise mark set in July 1978 by the Montreal Expos against Atlanta.

Pitching on his 33rd birthday, Scherzer (12-5) allowed one run over six innings and struck out nine to bring his total this year to 201 — his sixth consecutive season with at least 200, the longest active streak in the majors.

He contributed offensively with two walks and an infield hit.

"What a birthday gift! I wanted to get a win and a knock," he said. "Fifteen runs, a pitcher's best friend."

Harper chipped in with three hits and four RBIs while extending his career-best hitting streak to 19 games.

Travis Shaw and Lewis Brinson homered for the Brewers, who have lost nine of 11 to drop from first place in the NL Central.

"It's on to the next challenge," manager Craig Counsell said, referring to a weekend series against the division-leading Cubs in Milwaukee.

One positive for the Brewers in this one: Left fielder Hernan Perez pitched a scoreless eighth inning.